What is the recommended assessment and treatment plan for a patient with osteoarthritis (OA) in the right knee who is starting diclofenac (nonsteroidal anti-inflammatory drug (NSAID))?

Assessment and Plan for Right Knee Osteoarthritis with Diclofenac Trial

Assessment

Confirm the diagnosis of knee osteoarthritis through:

• Radiographic evidence of joint space narrowing, osteophytes, or subchondral sclerosis 1
• Clinical symptoms including pain with weight-bearing, morning stiffness, and functional limitation 2
• Baseline pain severity using WOMAC pain subscale to establish treatment response metrics 2

Critical pre-treatment screening before initiating diclofenac:

• Gastrointestinal risk factors: History of peptic ulcer disease, GI bleeding (especially within past year), GERD, or age ≥75 years 1
• Cardiovascular status: Current use of low-dose aspirin for cardioprotection, history of cardiovascular disease 1
• Renal function: Estimated glomerular filtration rate (eGFR) - oral NSAIDs are contraindicated if eGFR <30 mL/min and require careful consideration if eGFR 30-59 mL/min 1
• Concurrent medications: Document all acetaminophen-containing products including OTC cold remedies to avoid exceeding 4,000 mg/day total 1

Plan

Route Selection Based on Patient Age and Risk Profile

For patients ≥75 years old:

• Use topical diclofenac gel 4g four times daily rather than oral formulation due to substantially greater risk for cardiovascular, gastrointestinal, and renal adverse reactions with oral NSAIDs 3
• Topical diclofenac demonstrates equivalent efficacy to oral NSAIDs (effect size 0.91 vs placebo) while minimizing systemic exposure 3, 4

For patients <75 years old without contraindications:

• Oral diclofenac 50 mg twice daily or three times daily (100-150 mg/day total) for osteoarthritis 5
• Use the lowest effective dose for the shortest duration consistent with treatment goals 5

Gastroprotection Strategy

If patient has history of symptomatic or complicated upper GI ulcer but NO GI bleed in past year:

• Use either a COX-2 selective inhibitor OR nonselective NSAID (diclofenac) combined with a proton-pump inhibitor 1

If patient had upper GI bleed within the past year:

• Use COX-2 selective inhibitor combined with proton-pump inhibitor (diclofenac is not recommended in this scenario) 1

For chronic NSAID management in all patients:

• Consider adding a proton-pump inhibitor to reduce risk of symptomatic or complicated upper GI events, as this is cost-effective given current evidence 1

Special Cardiovascular Considerations

If patient takes low-dose aspirin (≤325 mg/day) for cardioprotection:

• Do NOT use ibuprofen due to pharmacodynamic interaction that renders aspirin less effective 1, 3
• Diclofenac does not demonstrate this same pharmacodynamic interaction and can be used with aspirin 1
• Strongly add a proton-pump inhibitor when combining diclofenac with aspirin 1

Monitoring and Follow-up

Assess treatment response at 2-4 weeks:

• Measure WOMAC pain subscale, physical function, and patient global assessment 2
• Diclofenac demonstrates statistically and clinically significant improvements by 2 weeks, with sustained benefit through 12 weeks 6, 2

Safety monitoring:

• Monitor for application site reactions with topical formulation (dryness in 36.6%, rash in 11.0% of patients) - these are typically self-limiting 2
• Assess for GI symptoms, edema, blood pressure changes, and renal function deterioration 1
• For long-term use beyond 12 weeks, safety data supports tolerability up to 1 year 7

If Inadequate Response to Diclofenac

Next steps if diclofenac fails after 4 weeks:

• Consider intraarticular corticosteroid injections 1
• Add tramadol, duloxetine, or intraarticular hyaluronan injections 1
• Refer for consideration of total joint arthroplasty if refractory to both nonpharmacologic and pharmacologic modalities 1

Important Caveats

Acetaminophen consideration:

• While guidelines recommend acetaminophen before NSAIDs, high-quality evidence shows acetaminophen provides no significant improvement over placebo in knee OA (P=0.92 at 2 weeks), whereas diclofenac demonstrates clear efficacy (P<0.001) 6
• If patient has already failed acetaminophen trial, proceed directly to diclofenac 1

Avoid nutritional supplements:

• Do not use chondroitin sulfate or glucosamine as they lack efficacy 1